9AM is the first hour of prayer [see Acts 2:15] when
the Temple gates opened. The Hebrew word for this hour of prayer is
"Shacharit"(morning). According to Jewish time this is the 3rd
hour (the third hour from sunrise); according to Roman time this is the 9th
hour (Roman time for each day began at 12 midnight).

The second hour of
prayer:

3PM is the second hour of prayer [Acts 3:1; 10:9].
The Hebrew word for this hour of prayer is "Minchah" (gift-offering). This
hour of prayer was known as the "hour of confession." The next day began at
sundown, or about 6PM. According to Jewish time this is the 9th hour; according
to Roman time this is the 15th hour.

Notice that the Jewish hours of prayer correspond to the
crucifixion of Jesus Christ. According to St. Mark, Jesus went to the cross at
the third hour, which in Jewish time corresponds to our 9AM [Mark 15:25].

The Hebrew word for the third hour of prayer is "Ma'ariv""Ma'ariv" or evening prayer began at sundown [hours of
prayer see Mishnah Berakhot]. According to the Jewish Book of Why,
volume I the "Ma'ariv" is a later addition, after the destruction of the Temple in 70AD. The Jewish Talmud records the late addition of the Ma'ariv service which
is not connected with the sacrificial system. [Jewish Book of Why, volume I,
page 148].